Centrifugal fan.



A. A. CRIQUI.

CENTRIFUGAL FAN.

AT'PLICATION FILED SEPT. 3. 1914.

Patented Nov. 30, 1915 ma. em J Zn A TTO/YNEY z m M w sra'rns ra'rnnr@FFICE.

\ p ALBERT A. CRIQUI, or BUFFALO, NEw'YoRK.

CENTRIFUGAL FAN.

Specification of Letters Patent.

Application filed September 3, 1914. Serial No. 860,024.

To all whom it may concern Be it known that I, ALBERT A. CRIQUI, acitizen of the United, States of America, and a resident of the city ofBuflalo, county of Erie, and State of New York, have invented certainnew and useful Improvements in Centrifugal Fans, of which the followingis a full, clear, and exact description.

My invention relates generally to a multiblade centrifugal fan of thetype in which a large number of blades are arranged in annular serlesaround a central space, open at one side for the entrance of the airwhich is drawn in through the central opening and forced outwardlythrough the spaces be tween the blades by centrifugal force. 7

My invention relates particularly to improvements in the formation ofthe blades,

which form part of the wheel of the centrifugal fan.. As is well knownto those skilled in the art, fans of this type are generally constructedto deliver air under pressure at a comparatively slow speed of rotation-In places where direct-connected fans, of this type, are installed and alow pressure of air is desired, it is necessary to run the fan wheel ata slow speed and a large frame motor is therefore required in order thata slow speed of rotation may be obtained. This is because of the factthat in most fan constructions inventors have sought to produce fans inwhich the velocity of the air leaving the wheel would be greater thanthe peripheral velocity of thewheel.

The general object of my invention has been, therefore, to provide a fanhaving a wheel with blades in which the velocity of the air leavingthewheel shall be less than the velocity of the periphery of the wheel,thereby producing'a low velocity-pressure at a comparatively high speedof rotation' snail-shaped casing is used in connection with the wheel,by means of which a portion of the velocity pressure of the air leavingthe wheel is converted into static pressure. And my wheel, in connectionwith its casing,

will produce a lower static pressure than asure of the discharge of theair along the entire length of the same, and/also one which shall pickup the air at a minimum loss by shock or lmpact with the entering air.

Another object has been to provide a blade the surfaces of which aredeveloped from twocones, having their curved surfaces tangent to eachother.

Each blade of my fan, as shown herein, has a forward curve at the heeland a backward curve at the tip. By reason of the backward curve at thetip the kinetic energy of the air as it leaves the tip is reduced to aminimum, thereby producing a low velocity pressure which is far lessthan that produced by the forwardly curved or straight surfaced type ofblade.

Throughout this description I use the term air as applied to my fan, butobviously the Same may be used for gases or other fluids and it is notintended to restrict this application to the use of air.

In my application for Letters Patent on improvements in centrifugalfans, filed Feb-- ruary 20, 1914, Serial No. 819,861, I have shown anddescribed a structure similar, in some respects, .to that herein shownand described. i

In the drawings which show an embodiment of my invention like charactersof reference indicate like parts throughout the the axis of thewheel andthe end of the tip farthest from the inlet precedes the end of the tipnearest to the inlet.

in Fig. 3 exceptthat the end of the tip of the blade farthest from theinlet follows the end of the tip nearest the inlet. Fig. 5 is an end'elevation of blade similar to those shown in Figs. 3 a d 4 and shows ina' diagrammatic manner a neans of ascertaining the pressures andvelocities of the air at the heel and tip of the blade. Fig. 6 is an endFig. f is an end elevation of a blade similar to that shown v elevationof a modified form of blade for a wheel having a diameter substantiallyequal at each end. Fig. 7 is a side elevation of the blade shown in Fig.6.

Referring to the drawings, 6 is the Wheel of my fan which is carried bya shaft 7, rotatably mounted in suitable bearings 8. For convenience ofillustration I have shown the shaft provided with a pulley 9 for drivingthe same but obviously an electric motor or any other suitabledirect-connected or belted means, may be used to furnish motive power tothe fan. The wheel 6 is inclosed within a snail-shaped casing 10, whichis provided with an inlet opening or eye 11 opposite to the inlet end ofthe wheel 6 and provided with an inlet cone 12, which directs the airfrom the exterior of the casing into the central opening of the wheel.The cas ing 10 is also provided with discharge opening 13.

The blades 14 of the wheel of my fan are secured laterally at one end toa disk 15, carried by hub 16 secured to the shaft 7.

a tangential An annular band or ring 17 is disposed at the. inlet end ofthe wheel and the outer ends of the blades, are secured thereto bysuitable means. In the ordinary type of fan, as is well known, thetendency of the entering air is to rush to the end farthest from theentrance and to be discharged from that part of the wheel, thus makingthe discharge at the entrance end of the wheel comparatively light. Inorder to take care of this inequality of the discharge at the tip of theblade,

2 along the tip and thus change the angle at which the air leaves thesame.

The blades of my fan are each developed from two cones, having theircurved surfaces tangent to each other, and is arranged so that thesurface of each blade is presented to the air at the heel of the bladeand the convex surface is presented to the air as it leaves the tip ofthe blade. Each of these blades may have its tip and heel coplanar ornon-coplanar with the axis of the wheel and may have the entrance end ofits tip and heel precede or follow the disk end thereof, as desired, tosuit the different conditions.

The-blades 14 of my fan are each developed from the two truncated conesA and B, which have their surfaces in contact are so arranged withrelation to each other that when the blade is wrapped around theirsurfaces, a smooth forward and backward curve is produced.

In Fig. 3 the blade 18 has its tip 19 noncoplanar with the axis 0 of thewheel and with its end 19, which isfarther from the axis in a radialdirection, preceded by the end 19",

I change the curvature of the blade" which is nearer the axis in aradial direction.

'The heel 23 of this blade is non-coplanar which is nearer the axis in aradial direction.

The blade shown in Fig. t has its tip 21 non-coplanar with the axis 0 ofthe wheel and has its end 21 which is farther from the axis in a radialdirection, preceded by the end 21*, which is nearer the axis in a radialdirection. The heel 22 of this blade is non-coplanar with the axis ofthe wheel and has its end 22*, which is farther from the axis in aradial direction, preceded by the end 22", which is nearer the axis in aradial direction.

Referring now to Fig. 5, where the pressures and velocities are showndiagrammatically, 2 1 is the tip of the blade and 25 the heel thereof.The end 24: of the tip, at the disk end of the wheel, is farther fromthe axis in a radial direction and the end 24 of the tip at the entranceend of the wheel is nearer the axis. The broken line 24 -0 representsthe lineal velocity of the tip of the blade at the end 24 The line 2al Drepresents the tangential line of discharge of the air as it leaves thetip of the blade at the end'2l of the tip of blade. The resultantvelocity of the air as it leaves the tip of the blade at the end 24 isindicated by the full line 24' -E. The line 24"C and the line 2t Drepresent respectively, the lineal velocity of the blade and thetangential discharge of the air as it leaves the tip of the the entranceend of the blade and the end 25 is at the disk end of.the blade. Thebroken line 25 c represents the lineal velocity of the end 25 at theheel of the blade and the broken line 25(Z represents the radialvelocity of the air passing from the blade at the end 25 The resultantvelocity of the blade at the end 25 is indicated by the full line 25 e.The lineal velocity of the blade at the end 25 of the heel is indicatedby the broken line 25(: and the radial velocity of the air passingthrough the blade at this end is indicated by the broken line 25"-cZ.The resultant velocity of the air at the end 25 of the blade isrepresented by the full line 25 e.

As hereinbefore pointed out, I may change the curvature of the blade atthe tip so as to equalize the discharge of the air along the same. Byreference to Fig. 5 it will be seen that the angle formed between theline 2P-C, representing the lineal velocity of the end 24 of the bladeand the line 24"D representing the tangential line of air disend is lessthan the angle formed'between the lines 2PC and 24*'D. The less theangle between the line representing the lineal velocity of the tip ofthe blade and the line representing the tangential discharge of the airfrom the blade the greater will be the resultant velocity of the air asit leaves the tip of the blade. Thus, it will be clearly seen that theresultant velocity represented by the line 24 -E at ,the end of the tip,which is nearer the axis in a radial direction is substantially equal tothe resultant velocity represented by the line 24*E at the end of thetip, which is farther from the axisin a radial direction, therebyequalizing the discharge along the tip .of the blade.

The blade 26 shown in Figs. 6 and 7 is for use on wheels where theentrance end' is substantially of the same diameter as the disk end. Theblade is developed from the surfaces of two truncatedcones and the tip27 thereof lies in planes which are parallel and coplanar with the axisof the wheel.

The heel 28 is non-coplanar and has its entrance end 28 preceded by itsdisk end 28*.

The curvature of the tip of this blade is changed so as to equalize theair discharge along its tip, as hereintofore described with reference tothe'blade shown in Fig. 5.

While I have shown and described my invention as applied to a fan havinga single wheel and a single inlet opening, it is obvious that it may beapplied to fans having a double'opening or to fans where two wheels areprovided, each with an inlet opening.

These and other modifications of the details herein shown and described"may be made without departing from the spirit of my inventionorthe'scopeof the appended claims.

Having thus described my invention, what I claim 1s:

1. A centrifugal fan having a wheel provided with a plurality of blades,the surface of each of said blades being made from a portion of thesurfaces of two cones, having their curved surfaces tangent to eachother, and the external diameter'at the disk end of said wheelbeingsubstantially the same as that at the entrance end thereof.

2. A centrifugalfan having a wheel provided with a plurality of blades,the surface of each of said blades being made from a portion of .thesurfaces of two cones, having their curved surfaces tangent to eachother, the tip' of each blade being substantially coplanar with the axisof said wheel and the heel of each of said blades being non-cosigned myWitnesses planar with the axis of said wheel, and the disk end of saidwheel being substantially the same in external diameter as that at theentrance end thereof.

' 3. A centrifugal fan having a wheel provided with a plurality ofblades, the surface of each of said blades being made from a portion ofthe surfaces of two cones, having their curved surfaces tangent to eachother 'the tip of each blade being substantially coplanar with the axisof said wheel, and the disk end of said wheel being substantially thesame in external diameter as that at the entrance end thereof.

4. A. centrifugal fan having a wheel provided with a plurality ofblades, the surface of "each of said blades being made from a portion ofthe surfaces of two cones, having their "curved surfaces tangent to eachother, the disk end of said wheel being substantially the-same inexternal diameter as that at the entranceend thereof, and the tipofeach" blade being so shaped that the angle formed between the linerepresenting the lineal velocity of the tip of the blade and the linerepresenting the tangential discharge of air from the blade increasesfrom the entrance end of the wheel toward the disk end thereof.

5. A centrifugal fan having a wheel proi vided with a plurality ofblades, the surfaces of each f said blades being made from a portion ofthe surfaces of two cones, and the tip of each blade being so shapedthat theangle formed between the line representmg the lineal velocityofthe tip ofthe blade Y and the line representing the tangential dischargeof air from the blade increases from the entrance end of said wheeltoward the disk end thereof.

6. A'centrifugal fan having a wheel provided with a plurality of blades,the surface of each of said blades beingmade from .a portion of thesurfaces of two cones, having their curved surfaces tangent to eachother, the heel of each of said blades being non-coplanar with the axisof said wheel, and the disk end of said wheel being substantially thesame in external diameter as that of the entrance end thereof. 7 Intestimony whereof, I have hereunto name in the presence of the twosubscribed witnesses.

ALBERT A. CRIQUI.

J. WM. ELLIS WALTER H. KELLEY.

